Large ions were discovered by P. Langevin and are sometimes referred to as "Langevin ions." Large ions have ion mobilities of the order of 10-8
per volt m-1
, or some 10 000 times lower than those of small ions. As a result these atmospheric ions contribute practically nothing to the conductivity
of the air, except in rare cases where small ions are nearly absent. Typically, they bear only a single electronic charge, as is true of small ions. Large ions move so slowly that they are not destroyed by being neutralized by still other large ions of paired signs, for such collisions are too infrequent. Instead, they are neutralized by union with a small ion of opposite sign. Their mean lifetimes are of the order of 15–20 minutes over the oceans, but may approach 1 h in very polluted air. The ion density
of large ions varies widely depending upon the degree of atmospheric pollution
. Representative low-altitude values might be 109
in clean country air, 1010
in an industrial area, and 108
over the oceans.
Wait, G. R., and Parkinson, W. D. 1951. Compendium of Meteorology. 120–121.
Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact firstname.lastname@example.org. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.